Project Summary Drug development for the central nervous system is a significant challenge due in part to the blood- brain barrier limiting the distribution of therapeutics into the brain. The thyromimetic sobetirome is one example of a drug with limited distribution into the CNS. However, there is great interest in thyromimetics like sobetirome in treating demyelinating disorders such as multiple sclerosis (MS) because thyroid hormone is known to stimulate differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes (OLs), the cells responsible for myelination in the CNS. Since the only clinical therapies for MS currently are immunomodulating in nature, the development of an agent that promotes myelin repair would represent a significant step forward in the field. While sobetirome itself primarily distributes to the peripheral tissues, a brain-selective prodrug of sobetirome could be designed to increase the brain exposure while concurrently limiting peripheral exposure. The long-term goal of this proposal is to develop a novel prodrug strategy for directing sobetirome into the brain by targeting the brain-resident enzyme fatty-acid amide hydrolase (FAAH). In order to examine a FAAH-targeted prodrug strategy, this research begins with the synthesis of a novel library of amide prodrugs of sobetirome inspired by the known structure-activity relationship for FAAH substrates. The role of FAAH will be evaluated in kinetic studies of prodrug cleavage using overexpressed enzyme and the effect on thyroid receptor activation will be done in cell culture experiments. Tissue distribution studies with prodrugs and sobetirome will be done in WT and FAAH-KO mice to determine the role FAAH plays in enhancing brain selectivity. Preliminary studies have established that FAAH-targeted sobetirome amide prodrugs can improve the brain selectivity over the parent drug by nearly 100-fold.